An endoscope is a medical device that allows physicians to capture images of and diagnose problems with internal body organs by inserting the device either through a natural orifice or a surgeon created opening and guiding it to a target site within a patient. In some cases, it may also be used to perform medical procedures on the internal body organs. It may be steerable so that its distal tip is controllably oriented and positioned for navigation purposes. An image capturing device such as a stereoscopic or monoscopic camera may be provided at its distal tip so that images captured by the camera from that perspective may be viewed on a display screen by the surgeon. To perform various medical procedures at the target site, surgical tools, such as those used for cutting, grasping, cauterizing, etc., may extend out of the endoscope's distal tip.
The endoscope may be rigid such as those used in laparoscopy or it may be flexible so that it is capable of following the curvatures of body lumens. It may also be rigidizable and/or robotic. A rigidizable endoscope is an endoscope that has at least one section of its flexible body that can be made substantially rigid by a mechanical locking mechanism. A robotic endoscope is a flexible endoscope that has at least one section that bends under a computer controlled servo mechanism.
Natural Orifice Transluminal Endoscopic Surgery (“NOTES”) may employ a steerable endoscope to perform surgical procedures on patients. As an example, a flexible endoscope may be guided through one of the body's orifices and enter the abdomen from the inside of the patient, rather than through a minimally invasive incision from the outside. For example, in “transgastric” surgery, instruments are passed through the mouth and into the stomach. A gastrotomy is then performed so that the instruments may enter the abdomen and be used by the surgeon to perform a medical procedure within the abdominal cavity. Once the procedure is completed, the instruments are withdrawn along with any tissue removed during the procedure, and the entry point is closed back up. Because no external incisions are made in the patient to accommodate entry of the endoscope, NOTES may be even less painful than surgery using minimally invasive incisions. Also, since it uses a natural body orifice instead of external incisions to enter the body, it may result in reduced needs for general anesthetics and faster recovery times.
During the operation of an endoscope, the endoscope tip may be turned multiple times and in different directions while moving towards, or while performing a medical procedure at, a target site. As a consequence, the orientation of images captured at the distal tip of the endoscope may change and it operator may become disoriented when viewing the captured images. If the operator accidentally moves the endoscope tip in the wrong direction as a result of such disorientation, the tip may inadvertently perforate or otherwise damage tissue causing harm to the patient. Even if such harm is avoided by carefully moving the endoscope tip, additional time is required to repeatedly ascertain the true orientation of the endoscope tip relative to the target site in the patient. Thus, the time required to perform the procedure is lengthened which adds to the cost of the surgery and increases health safety concerns.
U.S. Pat. No. 7,134,992 to Schara et al. (2006), which is incorporated herein by reference, discloses a method for presenting an endoscope image in a gravity referenced, upright orientation by sensing a rotation of the endoscope and rotating the endoscopic image accordingly to compensate for the sensed rotation before displaying the rotated image on a video display device.
One problem with such an image rotation technique is that when tools extend out of the distal end of the endoscope, they may not be oriented correctly from the operator's viewpoint of a captured image for the task at hand. Also, although it may be convenient to use gravity as a reference for orienting the image, it is desirable to eliminate the cost and complexity of additional hardware dedicated to sensing the direction of gravity. Further, it may be useful at times to provide the operator with a means to select a different orientational reference.